Airfoil structure



Nov. s, 1960 J. PAVLECKA 2,959,384

AIRFOIL STRUCTURE Filed Jan. 9, 195s 2 E my( @Y /7 42 INVEN TOR.'

Imm m n United States Patent FIL STRUCTURE John Pavlecka, 8797 Capital,Oak Park 37, Mich.

Filed Jan. 9, 1958, Ser. No. 708,339

20 Claims. (Cl. 244-124) This invention relates to a structure forhollow bodies consisting of a shell of an elongated profile and ofinternal supporting members, and which is particularly suitable forairfoil bodies such as airplane wings and control surfaces, helicopterrotor blades, etc.

The subject matter of this invention is the same as that of myapplication Serial No. 265,315 filed on I anuary 7, 1952, whichapplication was abandoned after its allowance, and is related to thesubject matter of my following applications: Airfoil Structure, SerialNo. 706,229, filed December 26, 1957; Airfoil Structure, Serial No.749,005, led July 16, 1958.

One object of this invention is to devise a shell type of structurehaving a smooth exterior and an inaccessible interior, the body of thestructure being integrated of a number of panel units each of which isan individual subassembly fabricated with full accessibility, and allthe subassemblies are held in rigid yet separable unity by linear keystelescoped into them through one end of the shell.

Another object is a shell structure in which a number of panel unitsprovide jointly both the shell and supporting members therefor, thepanel units having stress members such as stringers and spars integraltherewith, which members function also as carriers of key-engaging meansand of abutment means, and are interlocked by keys of a variable andnormally oversize shape sprung into their engaging means and urging themagainst one anothers abutment means by preloading forces so that theycoact as unitary supporting members for the shell.

A further object is a union of two or more panel units in a shell typeof structure by means of key-locked and relatively immovably constrainedstress members thereon, such locking and constraining duty beingperformed by a tubular key which is slit or interrupted in itsperiphery, the key being fitted into congruently interlitted protrudingarchways on the stress members with an interference by being normallylarger than the archways and being resiliently deformed thereby wherebyit draws the stress members by their archways into yabutment with oneanother at confronting faces alongside the archways.

Another object resides in devising a rigid union of three panel units orsubassemblies in a structure bearing key-locked stress members, such asstringers or spars or a combination thereof, the three stress memberscomplementing one another at radial planes around a key locking theminto unity, the key having a resiliently variable protile and drawingthe three members together by Ibeing confined with a change of itsprofile in them, thereby causing one or more of the members to be wedgedinbetween divergent planes on the others.

A still further object is an airfoil or similar shell structure in whicha closed profile end panel unit and two side panel units are heldtogether with preloading forces by means of stringers on theminterlocked by a resiliently confined key so that they function as aunitary spar, and in which opposedly alined stringers on the side panelunits apart Afrom the closed end are interlocked and held forcibly incontact with each other by another such key to provide another spar orspars in the structure.

Another object is an airfoil or similar shell structure in which twoside panel units and a movable control unit, such as an aileron, flap,or air brake, are cojoined into rigid unity by a resiliently constrictedkey in en- `gagement with two opposed stringers on the side panel unitsand with a third stringer or spar wedged inbetween them, the latterstringer or spar bearing hinge brackets mounting the movable controlunit.

A still further object resides in an airfoil or similar structure inwhich a number of panel units are secured into rigid yet separable unityby means of spanwise stringers or spars, the stringers or spars being incomplemental engagement with one another of segments around resilientlycontracted linear keys and being locked and constrained togetherthereby, both the panel units and the stringers or spars thereon beingbraced by chordwise ribs or bulkheads in their function as cooperatingsupporting members for the structure.

A comprehensive object is an airfoil or similar structure in whicheither one or both the leading and the trailing portions constituteindividual units or subassemblies, the latter one being either fixed ormovable as an aileron, and are each provided with a stringer or spar,and intervening dorsal and ventral panel units are provided withstringers along their vfore and aft edges which stringers bearconfronting faces on their inward side and bear angularly parted ordivergent faces on their outward side, and the Stringer or spar on theleading and on the trailing panel units bear convergent faces that arewedged inbetween theV divergent faces on the side panel unit stringersand are interlocked therewith by linear keys, the wedged conditionresulting from the keys being reduced resiliently in size to exertcompacting forces on the stringers or spars and thereby cause Vthem tocohere firmly at their faces.

These and other useful objects are attained through the principle ofdivision of a structure into individual units and their integration inthe manner herein disclosed, first with reference generally to all thefigures in the drawing which forms apart of this specification, and thenwith reference to each figure individually.

A structure such as an airfoil body has an elongated profile defined bytwo sides and two closed profile ends, one of which may be occupied byanother airfoil'body hinged to the main one, such as an aileron, a flap,a rudder, or an elevator; the interior of both of these bodies isinaccessible for fabrication in consequence of which the prevailingtechnique is to build in interior members individually and apply piecesof skin to them one at a time by riveting, mostly of the blind kind withone side out of view. According to my principle of subdivision, such abody is constructed of three or more subassemblies, each one complete initself, and all of them open for fabrication with full accessibility sothat resistance welding or adhesive bonding `can be substituted 'forriveting; all such subassemblies are locked together by linear keys sothat they form jointly not only the shell of the body but its supportingmembers aswell; these results are achieved through the use ofaparticular division of the components of the body of the structure, andthe use of linear keys of a normally oversize profile sprung into placewhereby preloading forces are introduced into the interlocked members tolock them together relatively immovably.

The division of such a body is effected along lengthwise or spanwiseparting lines located so thatfpreferably three panel units obtain, eachof which represents a portion of the shell and of the'interior stressmembers therein; one such panel unit constitutes one closed chordalextremity of the structure and two others provide portions of its sidesor the whole sides of the shell and stress members integral therewith; afourth panel unit may constitute either a xed other closed chordalextremity of the shell, or a body movably attached to and complementingthe side panel units; such a movable unit, as an aileron, elevator,etc., may not only employ the same manner ofattaching it to the sidepanel Aunits Vas the fixed unit, but its own body may also be integratedof a number of segmental subassemblies.

Each subassembly or panel unit carries on its inner side certainstructural members which include stringers or spars at and along paneledges and on some of them also stringers apart from the edges, and ribsor bulkheads extending chordwise between the stringers. The stringers orspars on each panel unit are the carriers of means for obtaining aslidable engagement, jointly with the stringers or spars on theassociated unit or units, with linear keys telescoped inbetween them; inthis manner the stringers or spars on a closed profile extremity panelunit and on two side panel units, complementally associated with oneanother at the parting lines and at a location or locations apart fromthem, are cojoined into unity; the stringers or spars so key-locked aswell as the keys themselves embody certain distinctive features thatcause them to cooperate as single stress members equivalent to the usualone-piece beams or spars.

One such feature resides in that the stringers or spars are formed withfaces along their key-engaging means, which faces assume confrontingpositions on each two stringers in opposed alinement or in juxtapositionwith each other; another feature resides in that when three stringers orspars on three associated panel units are interlocked by one key, two ofthe stringers have confronting faces thereon along one side of the keyand have angmlarly spaced apart faces thereon along the other side ofthe key; the third Stringer or spar, usually on the chordal extremitypanel unit or pivotally attached thereto, has convergent faces thereonalongside of its keyengaging means, and fits inbetween the divergentfaces on the two stringers while engaging the same key therewith; thepurpose of such confronting opposed faces on the stringers or spars andof such angular confronting faces thereon is to provide abutments of oneagainst the other or others and cause them to block one anotherrelatively immovably while engaging the key; yet another feature residesin constraining the abutted stringers or spars in a rigid and cohesiveunion by applying preloading forces to the abutted faces thereof; tothis end, the key is formed with a tubular resiliently contractibleprofile, and the key-engaging means on the stringers or spars is made tocontain the key in a contracted shape and size and be drawn by forces soproduced towards the key; such drawing action results in the stringersor spars abutting each other and being wedged against each otherforcibly at their confronting faces. Two opposed stringers so abuttedand two opposed stringers with a spar wedged therebetween, buttressed bychordal ribs or bulkheads, not only endow the structure with rigiditybut are competent to function as one-piece supporting members therefor.

The hereinabove disclosed structural principles are applicable to alarge variety of embodiments of which a number of exemplary ones areshown in the drawing and are described in the following text withreference to the figures therein.

In the drawing:

Fig. l is a profile view of an airplane Wing and its aileron each ofwhich is assembled of three panel units by two linear keys in the caseof the wing and one key in the aileron.

Fig. 2 is an exploded view of the components of the wing and of theaileron of Fig. l.

Fig. 3 is a partial sectional view of archways as the key engaging meanson stringers and spars pertaining 4 to the wing of Figs. 1 and 2, takenin the plane and direction indicated by arrows 3-3 in Fig. 2.

Fig. 4 is a profile view of a multiple spar wing and of the aileronthereof, each one consisting of three panel units supported as well asheld together by key-locked stringers and spars. V

Fig. 5 is a view of the paneliunits pertaining to the wing and to theaileron of Fig. 4, shown in a disassembled State.

Fig. 6 is a prole view of another airfoil body such as a wing or controlbody with a fixedly attached trailing portion, in which four panel unitsare key-locked to constitute the body and provide supporting memberstherein.

Fig. 7 is a view of the structural components which constitute theairfoil body of Fig. 6, shown in a disassembled state.

Fig. 7a is a fragmentary view of a modified spar alternate to the oneshown in Fig. 7.

Fig. 8 is a view of the underside of one of the side panel units and ofthe trailing end unit of Figs. 6, 7 and 7a, taken in Fig. 7 in the planeand direction indicated by arrows 8-8 therein, and showing the spacingof keyengaging archways on the stringers and spar therein.

Fig. 9 is a profile view of an airfoil structure such as a helicopterrotor blade, the shell and the stress members of which consist of threesubassemblies interlocked into unity by a single linear key.

Fig. 10 is a view of the individual components of the blade of Fig. 9shown in a disassembled relationship.

The wing and the aileron structures of Figs. 1 and 2 embody the sameprinciples of construction and assembly in that each one includes threepanel units which jointly form both its shell and internal stressmembers, and are held in unity in an identical manner; moreover, theaileron is attached to the wing in substantially the same manner as itsleading end unit; this unit includes a panel 2 the edges of which extendspanwise on opposite sides of the wing, and between them the panel iscontinuous around the wing leading portion; in edge-to-edge alinementwith this panel at two parting lines is a dorsal panel 1 and a ventralpanel 3, both of which terminate with spanwise edges at the aileron.Besides the panel 2 the leading unit includes a Stringer 10 which isbased on the marginal portions of its opposite sides and intervenesbetween them, in which respect it represents a spar; this spar and thepanel 2 form jointly a cellular member in the interior of which isdisposed a number of chordal bulkheads 11 abutted against the spar webs.The construction of the dorsal and of the ventral panel units 1 and 3 isthe same in that each one has two stringers, 4 and 5 on the former and 6and 7 on the latter, based on its inner face at and along its spanwiseedges, and a number of chordwise ribs such as 8 and 9, respectively,extending between the stringers and abutting them.

The profile of the side panel unit fore stringers 4 and 6, bothsubstantially alike, includes attaching flanges 12 and 13, dual walls i4and 1S standing thereon, shoulders 16 and 17 supported each on one ofthe Walls and connected with each other by a series of longitudinalarchways 18 to which the faces on the shoulders are directed radially.The aft stringers 5 and '7 on the same respective panels have a proleanalogous to that of the fore stringers 4 and 6, except in that theirrespective walls 19 and 20 support archways 21 and 26 directly in aradial position thereto without any shoulders, while their other walls,such as 22, support the archways `through the medium of shoulders 23 and24., respectively. The fore Stringer archways 1S and 25 and the aftStringer archways 23 and 24 are interrupted by lengthwise clearancespaces, and are staggered into complemental positions as shown in Fig.3; when assembled into the structure, the archways on each pair ofopposedly alined stringers 4 6 and 5 7 interfit congruently with oneanother and their respective shoulders 17 and 27, and 23 and 24, fallinto confronting positions of each other, while their respective annessishoulders 16 and 28, and walls 19 and 20, assume radially divergentdirections.

Both the leading panel unit 2 and the trailing unit as represented bythe movable aileron, are secured to the side panel units 1 and 3 bymeans of spars; the spar 10 in the leading panel unit 2 has a profiledefined by attaching anges 29 and 30 based on the opposite inner facesof the panel unit, lateral walls 31 and 32 projecting therefromconvergently and bearing a set of archways 33. The spar 34 for mountingthe Iaileron has a profile including lateral shoulders 35 and 36 inradially convergent directions and connected by archways 37; as shown inFig. 3, these archways have a length substantially equal to that of thearchways 21 and 26 on the associated stringways on each of the stringersand on the spar 34 are nominally twice as long as the archways so thatboth stringers and the spar interiit with one another into a coaxialalinement of their archways; the length and the spacing of the archwayson the two associa-ted fore stringers and spar 46-10 in the leading endof the wing are the same as on the stringers and spar shown in Fig. 3.

In the assembled wing, the fore stringers and spar 4-6-10 and the aftstringers and spar 5-7-34 intert congruently with each other and areinterlocked in that relationship by linear keys 38 and 39, respectively;the stringers and spars so interlocked confront each other with theirshoulders and walls and thereby block each other relatively immovablly;moreover, the keys 38 and 39 are oversize in their free shape and aresplit lengthwise so that when sprung into their place in the stringersand spars they exert distending force on the archways confining them andthereby draw the stringers and spars together; under this tension thestringers and the spar in each union abut each other forcibly at theirshoulders and walls and, furthermore, because of the convergent walls onthe spars and 34, these members are wedged inbetween the respectivedivergent stringers; such abutted and wedged unions in the wing of Fig.1 function as single rigid stress members or main spars for the wing.

The wing aft spar 34 mounts on the reverse side of its shoulders 35 and36 a number of brackets such as 40 to which the movable aileron or flapis hinged; the structure of this body corresponds to that of the wing,and consists of three panel units 41, 42 and 43 which constitute jointlyits shell as well as interior stress members; these members include aspar 44, stringers 45 and 46, and ribs 47, 48 and 49 buttressing them onthe respective panel units, The opposed stringers 45--46 on the sidepanel units confront each other at shoulders such as 50 on the aft sideof a row of interrupted archways on them, and on the fore side thereofare parted from each other between divergent shoulders such as 51. Theleading panel unit spar 44 has convergent shoulders 52 thereonsupporting its archways, which shoulders become wedged inbetween thestringers divergent ones as the two stringers and the spar jointlyengage with their archways a normally oversize key of a tubular splitcross-section with the same results as in the unions in the wing; at thetrailing aileron end screws 54er other equivalent means is employed tojoin the panel units 42 and 43 to a feather edge. For connecting theaileron or iiap pivotally to the wing, the leading panel unit ribs 47are hinged to the wing bracket-and-spar subassemblly 40-34.

The structure of the wing and that of its aileron or flap of Figs. 4 and5 is distinguished by the same features as the ones in the precedingfigures, the exceptions being certain modified Stringer and sparprofiles, and the use of two opposed stringers in a central location foradditional strength. The wing shell and its stress members are againcomposed of three panel units 55, 56 and 57 which are provided withrespective complementally grouped spar and stringers 58, 59 and 60 atthe leading prole end, and apart from it the dorsal and the ventralpanel units 56 and 57 are provided with stringers op- 6 posedly alinedin two pairs 61--62 and 63-64, the latter pair of which is associatedwith a spar 65 for supporting and pivotally mounting the yaileron orflap.

The spar 58 in the leading panel unit 55, and the bulkhead 66 abuttingit are analogous to those in the wing of Figs. l and 2, the spar againhaving the characteristic convergent walls 67 and 68 with archways 69thereon; its companion Stringer 59 on the dorsal panel unit 56 resemblesit in that it has convergent walls 70 and 71 to provide its abuttingfaces, and archways 72 on them. The other Stringer 60 on the ventralpanel unit 57 conforms closely to its counterpart 6 on the panel unit 3of Figs. 1 and 2, except in that its shoulders 73 and 74 astridearchways 75 are coplanar and in a forwardly in clined position. Whenassembled, the stringers 59-60 Iare face-to-face at their respectivewall 71 and shoulder 74, while their other wall and shoulder, 70 and 73,provide divergent faces inbetween which the spar convergent walls 67 and68 are drawn as the three sets of archways 69-72-75 are interfitted andinterlocked by a key 76 of ia resiliently contracted profile.

Stringers 61-62 jointly constitute a central spar in the wing; both are`of the same species, differing only in height; their profile includesarchways 77, two shoulders 78 therealong, lateral walls 79, and flanges80; the two stringers become abutted Shoulder-against-shoulder as a key81 of a resiliently reduced girth is telescoped into them; the tallerStringer 62 is buttressed by chordal ribs 82 and 83 which tie it withthe stringers 60 and 64 located at the panel unit edges. The dorsalpanel unit 56, because of predominant compressive stresses in it, isreinforced by spanwise stiifeners 84.

The Stringer -and spar trio 63-64-65 which holds the wing trailing endin unity as well as secures the aileron to it, is made up of certaintypes employed in this and in the preceding wing assemblies; theStringer 63 is identical with the Stringer 61 on the same panel unit,and the Stringer 64 is of the same type as the Stringer 5 of Figs. 1 and2 in that its inclined wall 85 and shoulder 86 provide its abutmentfaces; the profile of the spar 65 is related to that of the spar 34 ofFigs. 1 and 2 with convergent shoulders 87 and 88 astride a series ofarchways; it has a number of brackets such as 89 secured to it formounting the aileron pivotally. When assembled, the opposed stringers63-64 abut each other with their inward shoulders 86 and 90 while theirrespective wall and shoulder 85 and 91 form a divergent open Sector intowhich is wedged the spar 65 with its shoulders 87 and 88 as it engages aresiliently conned key 92 jointly with them.

The aileron or ap in this wing assembly also makes use of the three-unitconstruction, the panel units 93, 94 and 95 being held together withpreloading forces through the instrumentality of respective stringersand spar 96, 97 and 98, and a resiliently contracted key 99. However, incontrast to the aileron configuration of Figs. l and 2 the trailingportion of the shell and the stress members therein are provided in thiscase by a Single panel unit 95, while the leading shell portion and thestress members therein are constituted by the dorsal and the ventralpanel units 93 and 94. The spar 98 in the trailing panel unit 95,similarly as all the spars in the wing structures herein disclosed, ischaracterized by convergent walls astride its key-engaging means,represented in all the embodiments by interrupted protruding archways.The stringers 96 and 97, both of a similar profile, on the leading panelunits 93 and 94, respectively, are analogous to the Stringer 64 on theventral panel unit 57 in the wing in that their abutment faces areprovided by a shoulder and an inclined wall. The same wedged conditionof the end panel unit spar 98 between the abutted stringers 964497obtains as in the preceding such cases herein disclosed, due to the useof a tubular key 99 sprung into its place by resiliently deforming itsprofile.

For mounting the aileron or ilap on the wing, collars such `as 100, withlugs thereon are included at intervals 7 inbetween the interttedstringer and spar archways on the'key 99, and are secured immovably tothe key by pins orbolts `101; the lugs are attached pivotally to thebracketand-spar unit 89-65 in the wing.

The airfoil body of Figs. 6 and 7 consists of four panel units of which102, 103 and 104 provide' the leading portions, the dorsal and theventral side, respectively, and unit.105 complements them asa fixedtrailing portion; obviously, a movable control unit such as an aileron,elevator, etc., can be substituted for the xed one and secured to themain body in the same manner. Two linear keys 106 and 107 of an oversizeopen profile in their free condition interlock the units 102, 103 and104 into a rigid assembly; for this purpose two stringers 103 and 109run on and along the opposite marginal faces of the panel unit 102; eachof thesestringers is formed with two angularly related faces, one on ashoulder 110 and the other on a lateral wall 111, and with lengthwiseinterrupted archways between them. Bulkheads 113 abutting thesestringers give the panel unit its shape and transfer loads thereon toand into the stringers.

The dorsal panel unit 103 comprises two stringers 114 and 115 of aprofile analogous to that of the leading panel unit stringers 108 and109; a number of ribs such as 116 extend chordwise between the stringersas integral parts of the panel unit. The components of the ventral panelunit 104 include a Stringer 117 at and along the aft edge of a profilesimilar to that of its counterpart 115 on the dorsal panel unit, and aspar 11S at Iand along the fore edge; this spar, in addition to being acarrier of instrumentalities for cojoining the three panel units 102,103 and 104 into a. wedged relationship lat both the dorsal and ventralsides, functions also jointly with the stringers on the panel units andwith the interlocking keys which cause the wedged relationship, as themain spar in this structure.

The spar 118 may `be either a single-web beam as shown in Fig. 7, or abox beam shown in Fig. 7a as 11Sa, the essential features, i.e., twosets of archways 119 and 120, shoulders 121 and 122 astride one set, andshoulders 123 and 124 astride the other, being the same in either case;chordal ribs such as 125 extend between the spar 118 and the aftstringer 117 to complete the panel unit 104 as a rigid subassembly.

The shoulders 121 and 122 on the spar 118have divergent directionsmatching the convergent faces on the associated Stringer 109 on thepanel unit 102; when the archways 120 between them are intertted withthose on the Stringer 109, and with a split and normally oversizetubular key 107 in them, forces are exerted by it that urge the spar andStringer into a wedged contact with each other at their angularshoulders. The shoulders 123 and 124 at the upper extremity of the spar118 have the distinguishing convergent directions as on the spars in thepreceding embodiments; in the assembly, the stringers 108 and `114 abuteach other at the dorsal parting line with their faces 111 and theshoulders 123-124 on the spar 118 become wedged inbetween theirdivergent shoulders 110- 126 as the resiliently confined key 106 drawsthem together.

The same wedging action takes effect at the juncture of the fixedtrailing panel unit 105 with the side units 103 and `104 as spar 128 onthe former unit, with convergent lateral walls thereon, is drawn andconstrained relatively immovably inbetween divergently related walls onthe opposed stringers 115- 117 on the latter units in the presence of aresiliently constricted split tubular key 129 in the respective archways130-131--132 intertitted with each other congruently according, forinstance, to the arrangement shown in Fig. 8; the archways are all ofequal length and the clearance spaces between them are double theirlength, in which respect this arrangement is similar to that of Fig. 3.

Another embodiment of the principleof integrating a structure of panelsubassemblies by interlocking them and causing them toabut and be wedgedagainst one another, is illustrated in Figs. 9 and 10; in this case anairfoil such as a helicopter rotor blade is assembled of three panelunits which occupy complemental sectors around a linear key. Two panelunits, 133 and 134, jointly provide thc closed leading and trailingportions as well as the ventral side of the airfoil shell and the innerstress members therein, and the third unit 135 forms a segment of thedorsal side. The panel units have stringers or spars 136, 137 and 138,respectively, thereon and chordwise bulkheads 139, 140 and 141 bracingthem; all of the stringers or spars have their attaching angcs at andalong the panel unit edges; on two of them, 133 and 134, these edges areon opposite sides and the stringers 136 and 137 thereon aresubstantially of the same profile which includes an upright wall 142 atone edge and another wall 143 projecting in an inclined direction awayfrom the opposite edge, and both walls are connected by archways 144.The stringer 138 on the dorsal panel unit 135 is dened by convergentlateral walls and 146 connected by archways 147. In the assembledairfoil, the stringere 136- 137 are abutted with each other at theirupright walls 142 on one side of a key 148 at the ventral parting line,and their inclined walls 143 are parted divergently on the other keyside; inbetween the latter walls is drawn the Stringer 138 and its panelunit 135; as the key 143 interlocks the archways of the three stringers,it induces preloading forces at their confronting walls by thespringiness of its material and by its cross-sectional configuration;its cross-section is open on two diametrally opposite sides, and is ofan oversize free girth, similarly as in the keys in the precedingembodiments herein disclosed.

I claim:

1. In a panel, three structural units forming complemental portions ofthe structure, a stress member based on the surface of each of saidunits coextensively with the stress members on the other two units, alinear key interposed between said stress members, said stress membersoccupying three adjoining sectors around said key and having faces inconfronting positions of one another at said sectors and by and betweensaid faces bearing means for engaging said key slidably jointly with oneanother, at least two of said sectors and stress member faces thereatbeing convergent toward said key and confronting divergent faces on thestress members occupying adjoining sectors, and means as a part of theprofile of said key in cooperation with said stress members keyengagingmeans for subjecting said stress members to tensile forces and causingthem to abut against one another at said confronting faces thereof forrelatively irnmobility of said panel units.

2. In a structure, components and their relationships as set forth inclaim 1, said key-engaging means on said stress members residing inprotruding lengthwise interrupted archways intertted congruently withone another, and said key profile being tubular and being interrupted onat least one side thereof and being confined resiliently in saidarchways in a contracted size.

3. In a structure, three panel units meeting one another at twolengthwise parting lines to form a closed profile end and side portionsof a shell, a linear key in said shell coextensive with said partinglines intermediate thereof, three stress members based one on each ofsaid panel units at and along said parting lines and therefrom reachingto said key and bearing substantially radial faces therealong inconfronting positions of one another at three complemental sectorsaround said key, and means borne by said stress members for engagingsaid key slidably jointly with one another, said key being oversize andeffecting resiliently a change from the free size thereof to the size ofsaid stress member engaging means and thereby subjecting said engagingmeans and said stress members bearing the same to forces causing saidstress members to abut one another at said confronting faces thereon.

4. Ina structure, components and their relationships 9 as set forth inclaim 3, one of said stress members having walls based on the oppositesides of the panel unit forming said shell closed end and bearing saidfaces on said walls, two others of said stress members having each dualwalls based on one of the panel units forming said shell side portions,said two stress members bearing said faces on one of said dual wallsthereof in confronting positions with said closed panel unit stressmember faces and having shoulders borne on the other of said dual wallsthereof away from said closed shell end and providing said faces thereonin confronting positions of each other.

5. In a structure, two panel units forming opposite portions of a shell,stringers extending on said panel units in opposition to each other, alinear key interposed between said stringers, said stringers bearingmeans for slidably engaging said key jointly with each other and havingfaces in confronting positions of each other along one side of said keyand having faces parted divergently from each other along the other keyside, a spar having convergent faces thereon and by and between saidfaces bearing means in engagement of said key slidably jointly with saidstringers engaging means and being in confronting positions of saidconvergent faces thereof with said stringers divergent faces, and meansembodied in said key for exerting tensile forces on said stringer andspar engaging means and thereby drawing said stringers into abutmentwith each other at said confronting faces thereof and drawing said sparto be wedged inbetween said stringers divergent faces.

6. In a structure, two panel units forming portions of one side of ashell and meeting each other at a lengthwise parting line therein,stringers extending on said panel units at and along said parting line,a linear key interposed between said stringers at a distance from saidparting line, said stringers bearing means for slidably engaging saidkey jointly with each other and having faces in confronting positions ofeach other in a location between said parting line and said key, saidstringers having other faces parted divergently from each other alongthe side of said key away from said panel units, a spar havingconvergent faces thereon and by and between said faces bearing means forslidably engaging said key jointly with said stringers engaging meansand being in confronting positions of said convergent faces thereof withsaid stringers divergent faces, and means embodied in said key fo-rexerting tensile forces on said Stringer and spar engaging means andthereby drawing said stringers and said panel units thereof intoabutment with each other at said confronting faces thereof at saidparting line and drawing said spar to be wedged inbetween said stringersdivergent faces.

7. In a structure, three panel units forming an airfoil shell divided atthree spanwise parting lines, two of said parting lines extendingbetween all three of said panel units on one shell side and one partingline extending between two of said panel units on the other shell side,stringers based one on each of said panel units at and along therespective parting lines thereof, a linear key interposed between saidstringers in said shell, each of said stringers bearing faces convergentwith each other in a location between the panel unit thereof and saidkey and in confronting positions of the faces on the other twostringers, by and between said faces said stringers bearing means forengaging said key slidably jointly with one another, and means embodiedin said key for exerting tensile forces on said stringers through saidengaging means thereof and thereby drawing said stringers into abutmentwith each other at said confronting faces thereof and holding said panelunits cohesively at said parting lines therein.

8. In a structure, three panel units forming an airfoil shell, one ofsaid panel units providing a closed profile extremity of said shell andmeeting the other two panel units at spanwise parting lines on the sidesof said shell, a first pair of opposedly alined stringers extending oneStringer on each of said side panel units at and along said partinglines, another pair of opposedly alined stringers extending one Stringeron each of said side panel units at the other shell profile extremity, aspar based on the inner sides of said closed extremity panel unit at andalong said parting lines coextensively with said first pair ofstringers, linear keys interposed o-ne between said spar and said firstpair of stringers and another one between said other pair stringers,said spar and first pair stringers and said other pair stringers bearingmeans for engaging said keys slidably and bearing faces in confrontingpositions of one another along said keys, and means embodied as a partof the profile of said keys for exerting forces on said spar andStringer engaging means and thereby drawing said spar and said firstpair stringers together and drawing said other pair stringers togetherand causing them to abut one another at said confronting faces thereof.

9. In a structure, components and their relationships as set forth inclaim 8, a third pair of opposedly alined stringers extending oneStringer on each of said side panel units intermediate said iirst andother pairs, chordal ribs integral with at least one of said side panelunits extending between and abutting the stringers of said three pairson said unit, a linear key interposed between said stringers of saidthird pair, said stringers bearing means for engaging said key slidablyand bearing faces lin confronting positions of each other along saidkey, and means embodied as a part of the profile of said key forexerting forces on said Stringer engaging means and thereby drawing themtogether and causing them to abut at said confronting faces thereof.

10. In a structure, two panel units forming each one side of an airfoilshell, another panel unit forming a closed airfoil extremity of saidshell and meeting said side panel units at two spanwise parting lines onthe shell sides, a structural unit complementing said shell at the otherairfoil extremity, a first pair of opposed stringers extending oneStringer on each of said side panel units at and along said partinglines, another pair of opposed stringers extending one Stringer on eachof said side panel units at and along said other -airfoil extremity,linear keys interposed one between said stringers in each pair, saidstringers in each pair having confronting faces along one key side andhaving divergently parted faces along the key other side, two sparshaving convergent faces thereon, one of said spars being based on andintervening between the opposite inner sides of said closed extremitypanel unit at and along said parting lines and with said convergentfaces thereof confronting said iirst pair Stringer divergent faces, theother one of said spars bearing means for mounting said structural unitcomplementally to said shell and with said convergent faces thereofconfronting said other pair Stringer divergent faces, said spars andstringers confronting one.

another bearing means for engaging said respective keys slidably, andmeans embodied in the profile of said keys for exerting forces on saidstringers to cause them to abut each other at said confronting facesthereof and to cause each of said spars to be wedged inbetween saidstringers divergently parted faces.

1l. In a structure, components and their relationships as set forth inclaim 10, said structural unit complementing said shell at said otherairfoil extremity being another panel unit and meeting said side panelunits at spanwise parting lines on the shell sides, said other one ofsaid spars being based on and intervening between the opposite innersides of said complemental panel unit at and lalong said parting lines.

l2. In a structure, components and their relationships as set forth inclaim 10, said structural unit complementing said shell at said otherairfoil extremity being a pivotally movable body, said other one of saidspars bearing hinge brackets on the reverse side of said convergentfaces thereof and mounting said movable body pivotally thereon.

13. In a structure, two panel units forming each one side of an airfoilshell, another panel unit forming one closed airfoil extremity of saidshell and meeting said side panel units at two spanwise parting lines onthe shell sides, a structural unit complementing said shell at the otherairfoil extremity thereof, two stringers extending side-by-side one oneach of said panel units at and along one of said parting lines, astringer and a spar extending side-by-side each on one of said panelunits at and along the other one of said parting lines, two opposedstringers extending one on each of said side panels at and along saidother airfoil extremity, linear keys interposed one between saidstringers side-by-side, another one between said stringer and sparside-by-side and a third one between said opposed stringers, saidstringers side-by-side and said stringer and spar side-byside havingconfronting faces in a location between said panel units and said keys,said opposed stringers having confronting faces lalong one key side,said stringers sideby-side and said opposed stringers having divergentlyparted faces on the other key side away from said confronting facesthereof, said spar intervening between said stringers on said side panelunits and bearing convergent faces and confronting said divergent faceson said sideby-side stringers therewith, another spar extending in saidshell and bearing means for mounting said structural unit in said otherairfoil extremity and having convergent faces and confronting saidopposed stringers divergent faces therewith, said spars and stringersconfronting one another bearing means for engaging said respective keysslidably, and means embodied in the profile of said keys for exertingforces on said stringers to cause them to abut each other at saidconfronting faces thereof Iand to cause each of said spars to be wedgedin between said stringers divergently parted fac.

14. In -a structure, a number of panel units forming portions of ashell, stringers extending on said panel units and therefrom reachingtowards each other and bearing each a Set of lengthwise interruptedarchways coaxiallywith the other stringers archways, faces borne on saidstringers astride said archways thereof, said faces on at least one ofsaid stringers being convergent with each other and confrontingdivergent faces on the other of said stringers, and a linear key havinga normally oversize cross-section and being resiliently deformable, saidkey being sprung into engagement with said stringers archways andinterlocking said stringers and panel units thereof relatively immovablyby drawing said stringers into abutment at said confronting facesthereof.

15. In a structure, an airfoil shell having a complemental shell hingedpivotally thereto, two stringers extending each spanwise on one of thesides of said airfoil shell in opposition to each other, a sparcoextensive with said stringers on the side thereof toward saidcomplemental shell, hinge brackets mounted on said spar and therefromprojecting toward said complemental shell and having said shell hingedthereto, a linear key interposed between said stringers and said spar,said stringers and said spar bearing means for cojoint slidableengagement of said key, and faces borne on said stringers and on saidspar in confronting positions of one another, said stringers and saidspar being held by said engagement thereof with said key in abutment atsaid confronting faces thereof.

16. In a structure, a shell having an elongated profile, a panel formingone closed profile extremity of said shell, two other panels meetingsaid extremity panel at parting lines and forming the shell oppositesides, stringers eX- tending one on each of said side panels inopposition to each other and having walls based on said panels at andalong said parting lines, a spar extending on said extremity panel andhaving walls based on the opposite sides of said panel in confrontingpositions of said stringers walls, on said walls thereof said stringersand said spar bearing lengthwise interrupted archways andhaving saidarchways intertted congruently with one another, and a linear key in aslidable engagement with said interfitted archways, said stringers andsaid spar confronting walls being convergent in the direction towardsaid key and being held in abutment with each other by said keyengagement with said archways on said walls.

17. In a structure, a shell having an elongated profile, a panel formingone closed profile extremity of said shell, two other panels meetingsaid extremity panel at parting lines and forming the shell oppositesides, a linear key extending in said shell between said side panelsproximately to said parting lines, stringers extending one on each ofsaid side panels at and along said parting lines and reaching to saidkey and bearing shoulders therealong opposed to each other on the sideaway from said shell closed extremity, on the side of said key at saidextremity said stringers bearing shoulders divergently parted from eachother, a spar extending on said extremity panel and having wallsreaching convergently toward said key between said stringers divergentshoulders, and means borne on said stringers and on said spar forcojoint slidable engagement with said key, said spar being wedgedinbetween said stringers divergent shoulders and said stringers beingabutted against eachother at said opposed shoulders thereof by saidcojoint engagement with said key for relative immobility of said shellpanels.

18. In a structure, two panels forming portions of a shell, a linear keyextending in a distanced relationship to said panels, stringers basedone on each of said panels reaching to said key and bearing means forengaging said key slidably in conjunction with each other, faces borneon each of said stringers substantially radially to said key, said faceson both stringers confronting each other along one side of said key andbeing divergent from each other along the other key side, a structuralmember extending along said stringers divergent faces and bearing meansfor engaging said key slidably in conjunction with said stringers, andconvergent faces borne on said structural member in confrontingpositions of said stringers divergent faces, said stringers and saidstructural member being held in abutment with each -other at saidconfronting faces thereof by said key in said engaging means thereof.

19. In a structure, three panel units forming two sides and one closedprofile extremity of an airfoil shell, three stress members extendingone on each of said panel units Ain said shell at said extremitythereof, two of said stress members being in opposition to each otherand the third one being in a lateral relationship therewith, two stressmembers extending in opposition to each other one on each of said panelunits at the other shell extremity, a spar subject to external loadingextending in a lateral relationship to said two stress members in saidother shell extremity, linear keys interposed one between said threeystress members and another one between said two stress members andspar, means on said stress members and yon said spar engaging saidrespective keys slidably, and faces on said three stress members andfaces on said .two stress members and on said spar along said keys, said'three stress members and said two stress members and spar being held inabutment with each other at said confronting faces thereof by said keyin said engaging means thereof.

20. In a structure, components and their relationships as set forth inclaim 19, and chordal ribs extending on each one of said panel unitsbetween said stress members in opposition at said closed profileextremity and at said other extremity of said shell, said ribs abuttingsaid stress members of each panel unit and transferring loads imposedthereon and on said spar into said stress members.

References Cited in the tile of this patent UNITED STATES PATENTS1,988,085 Orlando Jan. 15, 1935 2,432,396 Earhart Dec. 9, 1947 2,644,553Cushman July`7, 1953

